The long term objective of this proposal is to determine the role of epidermal growth factor (EGF) and nerve growth factor (NGF) in gastric mucosal surface cells. Specific aims proposed are the determination of the effects of EGF and NGF on the Na+/H+ exchange mechanism in gastric mucosal surface cells; the effects of EGF and NGF on other ion fluxes in surface cells; the characteristics of the binding sites for EGF and NGF on surface cells; and finally the biochemical links between the binding phenomenon and the cellular ion flux response. The knowledge accumulated in the fulfillment of these specific aims should provide a better understanding of gastric cell behavior and promote the development of new and better agents for the treatment of gastric problems. The methods used to achieve the specific aims will include the use of radioisotope flux methodology, pH stat methods, and the use of metachromatic dye equilibrium techniques to study the Na+/H+ and HCO3-/Cl- exchange mechanisms. 125I-labelled EGF and NGF will be used to conduct the binding studies proposed. Vacuum filtratrion and centrifugation techniques will be employed to separate free and bound ligand and determine the specificity of binding sites. Proven receptor binding techniques from other systems will be used to optimize conditions of time, temperature, tissue concentration and saturability in an attempt to show that binding sites for EGF and NGF on surface cells are indicative of physiologically revelant receptors. Methods to determine phosphorylation of endogenous proteins, the changes in DNA production, and the levels of cyclic AMP and adenylate cyclase, will be employed to elucidate the link between receptor interaction and physiological response.